Orchid Diversity at Three Elevations in the Mountain Sandstone Plateaus of the Cordillera del CndorEcuador

Orchids comprise one of the largest families of flowering plants and have important roles in the total biomass, water balance, and nutrient cycling of tropical ecosystems; however, they are also one of the most endangered plant taxa. Because their diversity is strongly coupled to environmental factors, we hypothesize that local elevation can affect the diversity of these organisms. The purpose of this research was to compare the orchid species diversity at 1200, 1400, and 1700 m of elevation, corresponding to a sandstone plateau of the Cordillera del Condor that hosts a great orchid diversity. For each elevation, three plots of 0.1 ha were established. Each plot was subdivided into 25 subplots, and 8 were randomly selected, wherein all orchid species were counted and identified. The results obtained revealed the existence of 119 species belonging to 54 genera and a total of 867 individuals. The greatest diversity of species was found at an elevation of 1700 with 63 species, followed by 1400 m with 52 species, with the least diversity at an elevation of 1200 m with 39 species. Orchid composition differed significantly among the three elevations related to more humidity at higher elevations (e.g., 1700 m). More importantly, twenty-one species were the best candidate indicators of environmental conditions (e.g., Maxillaria grayi, Elleanthus oliganthus, Maxillaria mapiriensis, Stelis pittieri, Stelis ortegae) in this region. We conclude that orchid communities in sandstone plateau forests in the Shagmi Range of the Cordillera del Condor are mainly limited by elevation.